Power washing concrete

[Parc Ferme]

What is the minimum psi that will effectively power wash/evacuate concrete after acid etch and or grinding? Assuming the optimal tip.

Im trying to source an adequate pressure washer with out over buying.


Thanks!!

 

[LegacyIndustrial]

You are looking for a 3000 PSI unit or better.

 

[Parc Ferme]

Thanks for the reply!

 

[marty_p]

I have seen a 2,500 PSI unit work, but grab a 3K for a little more change. And above anything else, INSIST on a Honda engine -- at least 5 HP.

Good luck, and keep us posted!

 

[Edger]

At least 10hp would be my call.

 

[Az Scooter]

Interesting responses. Typically, the hp of an engine is directly related to the volume and pressure of the water coming out of the machine. The simplest way to figure it is that a 5 GPM machine at 3000 PSI, for a cold water washer requires a minimum of 15 hp. A 4 GPM at 3000 PSI requires 12 hp. That means that a 5 hp machine would be less then 2GPM at 3000 PSI, which sounds like a very slow way to clean, and the 10HP machine would not be much better.
Since the concrete is being acid washed, it should be relatively easy to clean. There are a couple of options that you can do to get it right. You could actually hire someone that does it for a living, because surprisingly, there is more to it then you would think. You could also go to the local rental yard and get one for the day. No one needs a $1500 machine sitting around that they are not going to use very frequently, especially if you can rent it for less then $100 a day.
If you insist on doing it yourself, and do not want to rent a machine, I would go with a 3@2000PSI machine, for the simple fact that you are a home owner. That is a good home owner size of machine. It will be about a 6 HP motor, and will not be the fastest and most efficient, but it will get the job done. Be warned, it would cost you about the same to hire someone as it would to rent the machine, maybe a little more.
BTW, if pressure washers sit too long, the seals get soft, and have to be replaced. They are designed for frequent use.

 

[MoonRise]

The higher the pressure and the higher the flow rate, the more area can be cleaned in a certain amount of time. That means being able to use a wide nozzle 'fan' to clean a larger swath in a shorter amount of time than a lower-powered unit could do.

Your call as to how much money you want to spend (buy or rent) and how much time you want to spend doing the job.

More 'power' (pressure AND flow rate) = faster cleaning but more $$$$

But for 'just' washing down some acid-etched concrete you are not really going to need a whole bunch of 'power'. You are just rinsing everything off.

Now if you were using the pressure washer to actually 'clean' the concrete ...

note: you can 'cut' into concrete with a high-enough pressure and a narrow enough (angle) tip with a pressure washer. A fool can destroy a wooden deck pretty quickly with a pressure washer. Just an FYI, in case you didn't realize just what 3000 psi or so and a narrow spray tip can do to surfaces.

 

[Edger]

With a hand wand and single jet you should use a 15 degree fan jet with a min. of 3000 psi pressure and about 3.5 to 4.5 gals of water flow (@ 3000psi). 10hp will get that flow at 2000 psi so AZ Scooter is right about 15hp (I forgot my original machines were only 2000psi).

You can rinse off acid etch with a hose, but if you want to get the white residue off nothing less than 3000 psi held reasonably close to the concrete will do it, I did many tests to find that out.

If you go for a rental machine a 3000 psi pump will put out anywhere between 1500 and 3000 depending on jet wear. As the hole gets bigger the pressure drops. The only way to tell is to have a pressure guage on the machine.

Unless you are an expert you will not evenly clean the floor with a hand wand, you need a rotary pressure washing head with two jets underneath that spin around like a lawn mower. It is all getting a bit too technical.